It is known that extrusion devices are used in order to generate a plastic melt. This plastic melt can be continued to use in different manners. Thus, it is for example possible to introduce the molten material into a cavity of an injection moulding device in order to generate corresponding components by injection moulding. Likewise, it is known that the molten material is provided for a so called blow extrusion method with which a blow film is extruded. In all cases it is necessary that at the end of the extruder the liquefied molten material is transported to the respective place of use via corresponding melt channels. These channels can be arbitrarily complex and particularly divide up to single channels.
It is a disadvantage with known solutions of the extrusion device that they involve a high effort for the change of material. Thus, a so called purge process has to be performed in case the change of material from a first molten material to a second molten material should occur. In case with a blow extrusion device a certain time a product with a blue film colour is produced and subsequently a change to a transparent film colour is desired, thus initially the blue film colour and the corresponding molten material has to be purged out from the single melt channels. Herefore, the extrusion device is already operated with the subsequent material until the largest part of the old material of the molten material is purged out.
Since with melt channels in the edge area of these melt channels the transport velocity is mainly equal zero, the old material so to say sticks and the purge process is very time consuming. With blow extrusion devices with a through-put of up to approximately 120 kg molten material per hour thereby a purge process can normally take 20 minutes up to 1.5 hours. For each film layer for which a change of material should occur this leads to 120 kg or more waste material of the molten material. With multiple film layers the amount is multiplied with the amount of the film layers even if only one single film layer is purged. Therewith, the rejection rates of up to 1000 kg can be achieved. Simultaneously, the purge time comprises a dead time for the machine in which no useable production can occur. Accordingly, the known extrusion device with a corresponding purge process is afflicted with significantly recognizable disadvantages concerning the time effort and concerning the resulting costs and the waste material.